By Drew Middleton; Drew Middleton is the military affairs columnist for The New York Times's syndicate service

LEAD: THE DAY ON WHICH Western Europe took the final step into the most disastrous war in history was a fine one in London. The sun was bright and warm on Sept. 3, 1939, and the sky that Sunday morning was cloudless. But the news from Poland was bad....

August 4, 1987, Tuesday

LEAD: DAY BY DAY, SOUTH KOREA'S turbulence marches across current headlines and through the news broadcasts. Half forgotten is that war in the early 1950's that established a viable country and laid the foundations of its present prosperity. ''Korea:...